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Background Non-tuberculous mycobacteria (NTM) are a rare cause of infectious tenosynovitis of the upper extremity. Using molecular methods, clinical microbiology laboratories are increasingly reporting identification down to the species level. Improved methods for speciation are revealing new insights into the clinical and epidemiologic features of rare NTM infections. Methods We encountered three cases of epidemiologically linked upper extremity NTM tenosynovitis associated with exposure to hurricane-damaged wood. We conducted whole genome sequencing to assess isolate relatedness followed by a literature review of NTM infections involving the upper extremity. Results Despite shared epidemiologic risk, the cases were caused by three distinct organisms. Two cases were rare infections caused by closely related but distinct species within the M. terrae complex that could not be differentiated by traditional methods. The third case was caused by M. intracellulare. An updated literature review focusing on articles using modern molecular speciation methods found that several species within M. terrae complex are increasingly reported as a cause of upper extremity tenosynovitis, often in association with environmental exposures. Conclusions These cases illustrate the importance of molecular methods for speciating phenotypically similar NTM, as well as the limitations of laboratory-based surveillance in detecting point-source outbreaks when the source is environmental and may involve multiple organisms.

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